1. Field of the Invention
This invention relates generally to magnetic recording hard disk drives, and more particularly to a disk drive with a dual-stage actuator for positioning the read/write heads.
2. Description of the Related Art
Magnetic recording hard disk drives with dual-stage actuators for positioning the read/write heads on the disks have been proposed. A rotary voice-coil-motor (VCM) is typically the primary actuator, with the secondary actuator attached to the VCM and the read/write heads attached to the secondary actuator. A servo control system receives servo positioning information read by the read/write heads from the data tracks and generates control signals to the primary and secondary actuators to maintain the heads on track and move them to the desired tracks for reading and writing of data. As in conventional single-stage actuator disk drives, each read/write head is attached to the end of a head carrier or air-bearing slider that rides on a cushion or bearing of air above the rotating disk. The slider is attached to a relatively flexible suspension that permits the slider to “pitch” and “roll” on the air bearing, with the suspension being attached to the end of the VCM actuator arm.
The secondary actuator is typically a piezoelectric, electrostatic or moving-coil type of “milliactuator” located on the VCM actuator arm for moving the suspension (a “moving-suspension” secondary actuator), or a “microactuator” located on the suspension for moving the slider (a “moving-slider” secondary actuator).
One of the problems in a dual-stage actuator disk drive is that when the primary actuator is activated, it generates a relatively large acceleration at the secondary actuator, causing secondary actuator vibration. For example, when a “seek” operation is performed by the primary actuator to move the read/write head from one track to another track, the large acceleration during the seek can cause the secondary actuator to vibrate, resulting in a longer seek time and thus degraded performance of the disk drive. Moreover, if the resonance of the secondary actuator shows up in the transfer function of the primary actuator, the performance of the servo control system can be degraded.
What is needed is a dual-stage actuator disk drive that eliminates or minimizes secondary actuator vibration and resonance caused by acceleration of the primary actuator.